US12535661B2ActiveUtilityA1

Optical system and image pickup apparatus having the same

59
Assignee: CANON KKPriority: Oct 20, 2021Filed: Oct 14, 2022Granted: Jan 27, 2026
Est. expiryOct 20, 2041(~15.3 yrs left)· nominal 20-yr term from priority
Inventors:KOBAYASHI KANA
G02B 13/004G02B 13/0035G02B 9/64G02B 13/0045
59
PatentIndex Score
0
Cited by
21
References
19
Claims

Abstract

An optical system consists of, in order from an object side to an image side, a lens unit including a plurality of lenses and a final lens having a negative refractive power. A lens surface on the image side of the final lens has an aspherical shape that includes a concave area near an optical axis and an inflection point. A predetermined condition is satisfied.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
         1 . An optical system comprising, a lens unit and a final lens having a negative refractive power disposed on an image side of the lens unit,
 wherein a lens surface on the image side of the final lens has an aspherical shape that includes a concave area near an optical axis of the optical system and an inflection point,   wherein the lens unit includes two cemented subunits, each cemented subunit being configured by cementing a positive lens and a negative lens,   wherein the total number of lenses disposed in the lens unit is seven or more, and   wherein the following inequality is satisfied:
   1.780< Nd< 2.500 
   
       where Nd is an average value of refractive indexes of all lenses included in the lens unit. 
     
     
         2 . The optical system according to  claim 1 , wherein the lens unit includes an aperture stop. 
     
     
         3 . The optical system according to  claim 2 , wherein the following inequality is satisfied:
   0.05< skd/TL< 0.15   
       where skd is a distance on the optical axis from the lens surface on the image side of the final lens to an image plane while the optical system is in an in-focus state at infinity, and TL is a distance on the optical axis from the aperture stop to the image plane while the optical system is in the in-focus state at infinity. 
     
     
         4 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   0.10< skd/H max<0.30   
       where skd is a distance on an optical axis from the lens surface on the image side of the final lens to an image plane while the optical system is in an in-focus state at infinity, and Hmax is a maximum image height on the image plane. 
     
     
         5 . The optical system according to  claim 2 , wherein the following inequality is satisfied:
   1.0< TL/D< 2.0   
       where TL is a distance on an optical axis from the aperture stop to an image plane while the optical system is in an in-focus state at infinity, and D is an aperture diameter of the aperture stop. 
     
     
         6 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   0.3< R 2 Gn/f< 3.0   
       where R2Gn is a paraxial radius of curvature of the lens surface on the image side of the final lens, and f is a focal length of the optical system. 
     
     
         7 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   1.0<lfGn/ fl< 1.8   
       where f is a focal length of the optical system, and fGn is a focal length of the final lens. 
     
     
         8 . The optical system according to  claim 1 , wherein the lens unit includes a lens having a negative refractive power closest to an object. 
     
     
         9 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   7.0< EA/skd< 13.0   
       where skd is a distance on an optical axis from the lens surface on the image side of the final lens to an image plane while the optical system is in an in-focus state at infinity, and EA is an effective diameter of the final lens. 
     
     
         10 . The optical system according to  claim 2 , wherein the following inequality is satisfied:
   0.50< TL/DL <0.95   
       where TL is a distance on an optical axis from the aperture stop to an image plane while the optical system is in an in-focus at infinity, and DL is a distance on the optical axis from a lens surface closest to the object to the image plane while the optical system is in an in-focus at infinity. 
     
     
         11 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   1.45<NdGn<1.65   
       where NdGn is a refractive index of the final lens. 
     
     
         12 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   1.75< Ndn< 2.50   
       where Ndn is a refractive index of a lens having the largest absolute value among refractive powers of lenses having negative refractive powers included in the lens units. 
     
     
         13 . The optical system according to  claim 1 , wherein the lens surface on the image side of the final lens has an aspherical shape having an extremal point. 
     
     
         14 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   0.60< fL/f< 0.95   
       where f is a focal length of the optical system, and fL is a focal length of the lens unit. 
     
     
         15 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   5°<|Θ f|< 65°
   
       where Θf is an angular aperture of a lens surface on an object side of the final lens. 
     
     
         16 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   40°<|Θ f|< 61°
   
       where Θf is an angular aperture of a lens surface on an object side of the final lens. 
     
     
         17 . The optical system according to  claim 1 , wherein the following inequality is satisfied:
   5°<|Θ r|< 65°
   
       where Θr is an angular aperture of the lens surface on the image side of the final lens. 
     
     
         18 . The optical system according to  claim 1 , wherein the inflection point is disposed at a peripheral portion on the lens surface on the image side of the final lens. 
     
     
         19 . An image pickup apparatus comprising:
 an optical system; and   an image sensor configured to receive an image formed by the optical system,   wherein the optical system comprises, a lens unit and a final lens having a negative refractive power disposed on an image side of the lens unit,   wherein a lens surface on the image side of the final lens has an aspherical shape that includes a concave area near an optical axis of the optical system and an inflection point,   wherein the lens unit includes two cemented subunits, each cemented subunit being configured by cementing a positive lens and a negative lens,   wherein the total number of lenses disposed in the lens unit is seven or more, and   wherein the following inequality is satisfied:
   1.780< Nd< 2.500 
   
       where Nd is an average value of refractive indexes of all lenses included in the lens unit.

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